Visualizing viable Mycobacterium tuberculosis in sputum to monitor isolation measures

•Discontinuing isolation for tuberculosis patients under treatment relies on the infectiousness of respiratory specimens.•Assessing the viability of Mycobacterium tuberculosis in sputum takes between 10 and 42 days in liquid media.•We adapted a commercialized kit (Live/Dead® BacLight™) to monitor the viability of bacilli in the sputa of 18 TB patients.•The viability test predicted accurately (specificity 100%), rapidly (<1 h) and at a low cost (<1 €) the result of cultures.•The viability test could help worldwide in the decision to maintain isolation measures.